In general, a photovoltaic device is a component for converting sunlight into electric energy by using a semiconductor. The photovoltaic device is composed substantially of unit cells. The unit cells are electrically connected in series to each other in the form of an integral module, thereby supplying high voltage to the outside thereof.
Based on a material used for the photovoltaic device, the photovoltaic device is largely divided into a silicon based photovoltaic device, a compound based photovoltaic device and an organic material based photovoltaic device. The silicon based photovoltaic device, according to a semiconductor phase, is divided into a single crystalline silicon photovoltaic device, a polycrystalline silicon photovoltaic device, and an amorphous silicon photovoltaic device.
In addition, based on the thickness of a semiconductor, the photovoltaic device is divided into a bulk (substrate) type photovoltaic device and a thin-film type photovoltaic device. The thin-film type photovoltaic device has its semiconductor layer having a thickness less than from several micrometers (μm) to several tens of μm. In the silicon based photovoltaic device, the single crystalline silicon photovoltaic device and the polycrystalline silicon photovoltaic device are included in the bulk type photovoltaic device. The amorphous silicon photovoltaic device is included in the thin-film type photovoltaic device.
The compound based photovoltaic device includes a bulk type photovoltaic device and a thin-film type photovoltaic device. The bulk type photovoltaic device includes Gallium Arsenide (GaAs) and Indium Phosphide (InP) of group III-V. The thin-film type photovoltaic device includes Cadmium Telluride (CdTe) of group II-VI and Copper Indium Diselenide (CuInSe2) of group I-III-VI. The organic based photovoltaic device is largely divided into an organic molecule type photovoltaic device and an organic and inorganic complex type photovoltaic device. In addition, the organic based photovoltaic device also includes a dye-sensitized photovoltaic device. Here, the organic molecule type photovoltaic device, the organic and inorganic complex type photovoltaic device and the dye-sensitized photovoltaic device are included in the thin-film type photovoltaic device.
In such a photovoltaic device, it is required to increase the photovoltaic conversion efficiency by reducing an ineffective area and by widening an effective area. Also, the photovoltaic device should be able to supply a required amount of voltage.